High quality images for the entertainment industry (theatrical motion pictures, television, special venues, and the like) have been primarily captured by traditional motion picture cameras, or film systems, due to the limitations possessed by video cameras. These limitations result from the video camera's internal processing of the electro-optical sensor image data that conforms it to existing video standards, and causes the image data available for further processing to be bandwidth limited. Therefore, reducing the effective dynamic range and detail of the three color image records captured by the sensor.
When originating with film for television, the images are captured by exposing the film in a motion picture camera (typically at 24 frames per second although not limited to this frame rate), and subsequently, chemically processing the film. The resultant film sequences are then transferred to the video domain on a machine, referred to in the art as a telecine. The telecine scans the film image and converts it to the appropriate electronic video standard signals.
In this conversion to a video signal, interactive tools are provided, by a system known as a color corrector, to manipulate the color and tone scales of the images to create the desired look (as perceived by the telecine operator and/or the customer) of a film image on the video system.
Film products are able to capture a wide exposure latitude or dynamic range of contrast in a scene. Details in the shadows or dark areas of a scene, plus the details of highlights or bright areas are captured well by film. In shooting (exposing) film, the cinematographer understands the latitude of film and uses lighting to make best usage of that latitude, knowing that the video transfer process will later allow him to select the limited final image contrast and content of the television image. This whole process of capturing a wide latitude record and subsequently processing and selecting the conversion into the final narrower latitude of the video domain (dependent on the video standard) is a significant advantage of film origination over video originated systems. The telecine transfer operation also permits some content "framing" of the images from the film. This includes zooming, panning and rotation during the scan operation to recompose the film image for the television frame.
A number of factors make film the current method for image capture for television. One major factor is the creativity available in the color correction operation described above. The user has the ability to carefully and interactively decide how shadows, highlights, mid-tones, skin tones and other color objects will look on the final television image. Another factor is film's ability to maintain image detail in the extremes of the dynamic range which can be recovered should the film be incorrectly exposed, or if factors in the scene cannot be controlled, such as those in which scene content includes both bright highlights (e.g. detail in a white satin dress) and shadows (e.g. detail in dark wood).
Video systems (that is, traditional prior art electronic motion image capture systems), on the other hand, have a more limited dynamic range or contrast ratio. Video camera systems and associated recording/transmission systems only manage a narrow contrast ratio. Often image color detail in dark shadows and/or bright highlights is lost ("crushed" blacks and/or "clipped highlights") by the video process. This limited dynamic range is no longer necessarily a result of video camera and recording technology, however. Rather, the present inventions have recognized that the limitations are imposed by requiring the recording signal color metric to be "TV display ready" or "rendered" for the TV display.
When images are captured using a video camera (which captures/processes a motion image electrical signal) and recorder, the system is designed to process the signals and provide a finished image within the bandwidth limitations of a specific television/video standard (which is inherent in the design of the particular camera-recorder system, for example ITU-R Rec. 601-3, ANSI/SMPTE 274M-1995, etc.). In addition to the processing implemented to meet the signal/recording requirements of a specified video standard, video cameras also provide various types of controls to achieve the image "look" desired by a user. In a simple camera, this may just be white balance. Other controls such as brightness (exposure), gamma (contrast), and color matrixing could also be provided. Some sophisticated cameras may provide a range of "knee" point/slope settings (tone scale manipulation), filtering and various image processing controls to adjust the image being recorded. However, all these adjustments must be made on the camera before the images are captured, and are of a "trial-and-error" type. Image quality, therefore, relies on the user's knowledge and experience.
In practice, the image recorded by the video camera systems is recorded to a defined video display standard, and as such, contains less image information capacity relative to what is captured by the video camera sensors. Factors in the design and specification of these video standards (gamma correction, color sub-sampling, compression, etc.) result in the amount of image information available for creating special effects, theatrical images--and even television--being relatively limited. Often, after capturing the video images, the users may wish to adjust the images with color corrector tools similar to those described above in the telecine process, only in this situation the images are coming from a video source (e.g. video tape). The range of adjustments that can be made to the video originated images is limited since the color metric used to record the video signals at the time of image capture is rendered for the TV display. Thus, the creativity gamut of this process is considerably less than available using film and a telecine machine. Since video standards are also not compatible with each other (component vs. composite video, NTSC vs. PAL, standard versus digital high definition, etc.), the quality of the images produced when converting from a lower to a higher order video standard/format results in a lower quality image (e.g. artifacts).
While the sensors inside a digital video camera are generally able to capture a wide dynamic range (some approaching the dynamic range/resolution of negative film), this is reduced by the processing in the camera down to a range that can be recorded in a standard video format signal (e.g. ITU-R Rec. 601-3). Various user controls, internal setups, automatic functions and processing occur to scale the range of image information the sensor captures down to the image extent of the specific video format (standard) to be recorded/transmitted. These operations can include black and white level clamping or clipping, gamma adjustments, white balancing, "knee" adjustments and more. Even when these operations are performed in the digital video domain, the amount of image information available for creative manipulation or producing high quality images (e.g. theatrical motion pictures) recorded with a digital camera (whether analog or digital) is limited relative to what is achievable with film.
It would be desirable then to provide a means, by which original scenes can be captured using electronic digital motion cameras as an alternative to video, to simulate the imaging benefits produced with a traditional motion picture camera/film/processor system. Capturing the image information in a "data-type" format, independent of any particular video format/standard, would also allow for the same type of compatibility encountered when converting film images to any video format, as well as flexibility when transferring to other imaging media requiring a higher level of image fidelity (e.g. theatrical film images) than is currently available from any digital video technology. In addition, it would be desirable to provide a processing step that would further apply a set of algorithms to the captured "latent" image data to "develop" a digital image record simulating the attributes of the optical image of a motion picture film. The image data record produced by applying the present invention could then be manipulated for "creative effects" by currently utilized post-production tools (e.g. color corrector previously mentioned) employed with motion images captured on film.